Fix #765: Include disc number in Subsonic responses

See merge request !681

Cherry pick develop

See merge request !680

Fix #735: library view doesn't like long titles names

Closes #735

See merge request funkwhale/funkwhale!640

Fix #737: delivering of local activities causing unintended side effects, such as rollbacking changes

Deleted developers/index.rst, developers/subsonic.rst files

Fix #751: saving moderation policy when clicking on "Cancel"

See merge request funkwhale/funkwhale!662

Fixed #652: escaping issues in translated strings

See merge request funkwhale/funkwhale!658

Fixed a crash when federating a track with unspecified position

See merge request funkwhale/funkwhale!652

Fix #745: Added documentation to set up let's encrypt certificate

See merge request funkwhale/funkwhale!651

Fixed wrong proxy config file in docker documentation

See merge request funkwhale/funkwhale!650

Fix #743: Do not send notification when rejecting a follow on a local library

See merge request funkwhale/funkwhale!649

Fix #729: Display new notifications immediatly on notifications page

See merge request funkwhale/funkwhale!648

Fix #716: constant and unpredictable reordering during file upload

See merge request funkwhale/funkwhale!647

Fix #713: Added documentation on mono-container docker upgrade

See merge request funkwhale/funkwhale!646

Added link/documentation for Mobydick

See merge request funkwhale/funkwhale!630

Fix #707: Fixed cards display issues on medium/small screens

See merge request funkwhale/funkwhale!614